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Premium Passive Loudspeaker Crossover Components

Mivera

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I thought I'd start a section on premium passive crossover components I've used in the past and believe are top performers.

I'll kick things off with the Mundorf Zero ohm coil. This is the finest inductor in existence to my knowledge for frequencies under around 400hz. Above that air cores are the way to go. The problem with air core's is when we get to the lower frequencies, they need to get so big that the added DCR becomes more of an detriment than the benefits they bring. These incredible inductors are what put Mundorf on the map. Their DCR is so low, it's almost like nothing in the signal path at all. It's almost like going active without needing the extra amp channels!


ZFW-5042414.jpg

Zero Ohm coil N 300

The Zero-Ohm-Coil (ZOC) is a special form of transformer core coil.This is also made of the top quality material FERON. In the ZOC, an air gap is calibrated and adjusted by hand between the two laminated cores (one I-shaped and one E-shaped). The air gap determines the inductivity of the coil and demands great care in the manufacturing process. It must not be too small, as saturation effects would otherwise occur at high loadings. The high production complexity of the ZOC is always justifi ed when maximum faithfulness in pulse reproduction is required. With our ZOC, internal resistances are possible that cannot be achieved with other coils. Vacuum impregnation is absolutely recommended for zero-ohm-coils because it increases yet further the audible quality, making the most of the product engineering.

Check out the DCR specs on the N390!

N-390.jpg
 
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Mivera

Mivera

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There's been a lot of talk about the crossover in the JBL 4367 lately. This speaker has 2 separate boards for mid/high and woofer. Let's have a look at the woofer board for now seeing as we are on the woofer inductor topic:

JBL_4367-17.jpg

From what I read the woofer crosses over to the mid at 700hz with this speaker. Looks like we have a 4th order crossover here with 2 air core inductors with approx 18 gauge copper wire, with 2 electrolytic caps bypassed by 2 poly film caps. Since the crossover point is quite high, using air cores isn't too bad, but still there's a lot of DCR in the signal path of the woofer. This is going to gobble up amp power as well as reduce the amps grip on the woofer.

Based on a quick and dirty calculation, I get values of 3.4 mh on the left inductor, and 1.7mh on the right. Lets assume the copper grade is the same as what Jantzen of Denmark uses on their 18 gauge air cores and see what we get for DCR:

jantzen.jpg


Well they don't have a 3.4, but they have a 3.5 which is close enough. The 3.5 DCR is 1,10 ohms. Based on the difference between the 3.5 and 3.3, the 3.4 should be about 1.07 ohms. Now lets add the 1.7mh DCR of 0.72 and we have a total of 1.79 ohms of resistance in the signal path of the woofer!! This is definitely enough to make a huge impact on bass performance in my experience.

Now lets compare if the Mundorf zero ohm units were used instead. They don't have 3.4's or 1.7's on my posted list, but they have 1.8's and 3.9's. The 1.8's have a DCR 0.02 ohms and the 3.8' have a DCR of 0.03 ohms for a grand total of 0.05 ohms.

So we can have 1.79 ohms in the signal path gobbling up amp power, and causing the amps to lose their grip on the woofers, or we can have 0.05 ohms which is pretty much nothing. I think even the biggest of skeptic's should be able to understand why the Mundorf zero ohm inductors would be the better choice.
 
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amirm

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If you changed the inductor for Mundorf, that would change the RC time constant of the filter and hence change the crossover design, yes?

Second, the Mundorf "zero ohm" inductors have a core:

mcoil_n.png


By using that they are able to reduce the number of turns and hence get lower dc resistance. That core has hysteresis effect. Yes they say their have reduced this by hand making them but still, all else being equal, it is not the same performance as an air core. I rather pump more amplifier power into a speaker than to use a compromise to increase its efficiency. Tell me where I have gone wrong in this analysis :).
 
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Mivera

Mivera

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If you changed the inductor for Mundorf, that would change the RC time constant of the filter and hence change the crossover design, yes?

Second, the Mundorf "zero ohm" inductors have a core:

mcoil_n.png


By using that they are able to reduce the number of turns and hence get lower dc resistance. That core has hysteresis effect. Yes they say their have reduced this by hand making them but still, all else being equal, it is not the same performance as an air core. I rather pump more amplifier power into a speaker than to use a compromise to increase its efficiency. Tell me where I have gone wrong in this analysis :).

Yes a speaker is a balance of compromises. When crossing over @ 700hz you are forced to either put a bunch of DCR into the chain, or use a inductor with a core for far less DCR. The hysteresis effect is more of a problem with lower end cored inductors anyways. But such a large change in DCR will change the total system tuning so I wouldn't recommend the upgrade. Better to engineer upgrades into a system when designing it for best results. In the case of this JBL, I would stick to just cap and resistor upgrades, unless copper foil air core inductors with the same DCR can be found to replace the cheap wire ones.

But those 20 cent electrolytic caps should bite the dust. The fact they bypassed them with poly caps shows even JBL acknowledges that poly caps are better than electrolytic. But adding that extra $2 to the BOM to make them just 100% poly would have upset the balance sheet. Especially on a pair of speakers only costing $15000.
 

iridium

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Why not use 8 gauge or 10 gauge air core? That is a rhetorical question: why $$$$$$$$$$ left out of executives pockets!

iridium.
 

amirm

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But those 20 cent electrolytic caps should bite the dust. The fact they bypassed them with poly caps shows even JBL acknowledges that poly caps are better than electrolytic. But adding that extra $2 to the BOM to make them just 100% poly would have upset the balance sheet. Especially on a pair of speakers only costing $15000.
Using different type caps is a very effective technique for widening the frequency range during which minimum ESR is achieved. See this video on why we do that:


How will you achieve the same with using the same type cap?
 
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Mivera

Mivera

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Using different type caps is a very effective technique for widening the frequency range during which minimum ESR is achieved. See this video on why we do that:


How will you achieve the same with using the same type cap?

Why didn't they do that on the more critical mid/tweeter section then? I also use bypass caps. But I use very good film caps bypassed by even better film caps. The Mundorf caps are built like that internally anyways.

image.jpg
 
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Mivera

Mivera

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Why not use 8 gauge or 10 gauge air core? That is a rhetorical question: why $$$$$$$$$$ left out of executives pockets!

iridium.

It would be a sin to acknowledge that cost was a factor in determining the components chosen for this speaker.

Let's look at the DCR ratings on the minimum standard of air core inductor I use in my speakers

Screen Shot 2016-03-21 at 9.32.58 AM.jpg
 
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Mivera

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Thomas savage

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if they were easy to get to, i would do my resistors now. will think about it, cant physically fit the mundorf caps i wanted in the vivid. there might be a external x-over in the works though and that will make it much easier!!
 
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Mivera

Mivera

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This brings us to the next segment of the crossover, the resistor. Not only is this the easiest swap, it can be the most rewarding. Especially when upgrading those dreadful sand cast ceramic wire wound types.

bennic res.jpg


As far as the best I've tried price/performance wise, the Mills MRA 12 are a very big upgrade for most networks. And only $4.40 each from Soniccraft. Parts Connexion also sells them.

mills.jpg


mra.jpg

mra.jpg


For the ultimate in transparency go with the Dueland CAST unit's. They are the next best thing to no resistor at all in the signal path.

New from DUELUND, a step up from their standard resistors are their amazing CAST resistors. Constructed from a graphite rod with silver terminals in a phenolic cylinder for protection, using a high temperature epoxy, both as a cavity-fill within the cylinder, and to encapsulate the graphite element. This gives each part incredible mechanical stability, and incredible damping properties. They have practically zero inductance, with a 5% tolerance.The special charcteristic about this resistor is that it displays a negative temperature coefficient. For example, when the voice coil of a speaker heats up, it's impedance rises. The DUELUND Graphite Resistor counteracts this by means of a decreasing impedance. The results are greatly improved dynamics from the driver.

duelund-cast-resistor-350.jpg

http://www.partsconnexion.com/resistors_duelund_cast.html

Although the ultimate, the biggest pain with them is their size. They are very long and hard to fit on tiny low end PCB's.
 
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Mivera

Mivera

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if they were easy to get to, i would do my resistors now. will think about it, cant physically fit the mundorf caps i wanted in the vivid. there might be a external x-over in the works though and that will make it much easier!!

If you really want to do it up right, just build a new network from scratch on an external platform. The cost/performance you will get out of it will be far beyond any other tweak you will ever do to your system. For now swapping out the resistors with the Mills MRA-12's would be very easy on the standard board.

Great source for these parts in the UK. they sell both the Mills and Duelands:

http://www.hificollective.co.uk/components/mills.html

http://www.hificollective.co.uk/components/duelund_cast_resistors.html
 
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Mivera

Mivera

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resistors are cheap so would go with the cast if they fit. even dic thinks this might help.

what about metal film resistors?

Metal films (although triple the cost of the Bennics in the stock Vivid's) are cheaper than the Mills at 60 cents each vs $4.40 each, of the mills. However they are not near as good as the mills. The green ones on the left are metal films. The green ones on the right are different much better wire wounds from North that kill the green metal films on the left and are in the league of the Mills. If you look very close there's an MRA-12 in the box as well.

IMG_4134.jpg
 
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Mivera

Mivera

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mike what do you think about external networks\x-overs? this will be a option for me in near future.

It's better to do that, but the problem with the Vivid is it's a 4th order crossover, and a 4 way speaker. So there's tons of parts. You will just have to be very careful matching the DCR's of the inductors. You will have to measure the DCR of each one and find a a copper foil unit that matches, or just forget about the inductors and only upgrade resistors/caps.
 

Thomas savage

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It's better to do that, but the problem with the Vivid is it's a 4th order crossover, and a 4 way speaker. So there's tons of parts. You will just have to be very careful matching the DCR's of the inductors. You will have to measure the DCR of each one and find a a copper foil unit that matches, or just forget about the inductors and only upgrade resistors/caps.
yea well the external option will be official (its a secret so dont tell anyone:eek::eek::oops:) so i if i take advantage of this when its ready i will get the parts upgraded too. i won't bother with upgrading inductors though.
 
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Mivera

Mivera

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yea well the external option will be official (its a secret so dont tell anyone:eek::eek::oops:) so i if i take advantage of this when its ready i will get the parts upgraded too. i won't bother with upgrading inductors though.

Good choice but keep in mind that there's no 1 best cap. Unless you want to spend thousands on a massive inventory of caps to try, I would take tony's cap test seriously as I have found his assessment's to be very accurate.

http://www.humblehomemadehifi.com/Cap.html

And definitely use bypass caps on at minimum the tweeter. The best bypass cap I know of is this:

http://www.partsconnexion.com/cap_film_duel_bypass.html

However expensive so look at some of Tony's recommendations for cheaper options. I see he hasn't even tested this one yet.
 

AJ Soundfield

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Since the crossover point is quite high, using air cores isn't too bad, but still there's a lot of DCR in the signal path of the woofer. This is going to gobble up amp power as well as reduce the amps grip on the woofer.
Umm, no. The DCR of the inductor is a tiny fraction of the thing it's connected to, the woofer. It's clear you don't understand filter design. It will do neither of what you posited, sorry.
Boutique parts are good for audiophiles psychologically, but for the actual soundfield not so much. Amirs cap test link provided some nice insight there.
Do you understand that both your main and "bypass" cap is very much still in the signal path?

cheers,

AJ
 
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